Interesting that the range goes 6" in either direction from the median value. A 30" or 14" bass drum wouldn't be unimaginable but it seems like 22" is all the averages, if you round up the mean! There must be something about that size in particular.

I know pretty much jack shit about drum equipment compared to most on here.

I would have said the 'standard' bass drum size is a 22" just from the number of times I've seen 22" compared to any other.